confusion on full process of setting up heroku postgresdb for python app

so I have followed this guide https://devcenter.heroku.com/articles/connecting-heroku-postgres#connecting-in-python and provisioned a database for my heroku app. In my server code, I added the database url and ssl require. However, how does my server actually get permission to write to the database? Locally, with psycopg2 you would have : conn = psycopg2.connect(database="dbName", user = "postgres", password = "password", host = "127.0.0.1", port = "5432"), and thats how your server authenticates itself and has permission to write onto the postgres db. With heroku however, none of that extra information is provided except for the db url link. What is the remaining process that I must to do to allow my server deployed on heroku to have permission to write to its associated provisioned database?